1. Field of the Invention
Embodiments of the present invention relate to an electric power converter for rolling stock, mounted on rolling stock.
2. Background Art
An electric power converter for rolling stock of this kind is known, which has the following structure (see, for example, Japanese Patent Document No. JP-A-2005-223277). In the structure, a case containing electric components, such as semiconductor devices, is arranged beneath the floor of rolling stock and, onto the top plate of the case, a heat pipe of a zigzag thin pipe is connected which has a plurality of projections and in which a cooling medium is enclosed. At the end of the heat pipe of the zigzag thin pipe, a heat radiating fin is connected.
Such a structure is provided so that the inside of an electric power converter for rolling stock is cooled by the heat radiating fin through the heat pipe of zigzag thin pipe and the cooling medium.
Moreover, as an electric power converter for rolling stock having another structure of a cooling system formed, an electric power converter is known which has the following structure (see, for example, Japanese Patent Document JP-A-2004-140894).
In the structure, semiconductor devices converting electric power are contained in a case, in a part of which a cooling wind tunnel is provided through which a cooling wind flows. Onto a partition dividing the cooling wind tunnel, a plurality of semiconductor device cooling units whose heat radiating sections face the cooling wind tunnel are mounted with gaskets put in between. This provides the cooling wind tunnel and an electrical component mounting section so that they are divided and watertight.
However, in the example of a related electric power converter for rolling stock described in JP-A-2005-223277, onto the top plate of the case containing electric components such as semiconductor devices, the heat pipe of the zigzag thin pipe is directly connected to cool the electric components. Thus, there is no need to secure watertightness. But there is still an unsolved problem in that the heat pipe of zigzag thin pipe is expensive to increase the manufacturing cost of an electric power converter for rolling stock.
Compared with this, in the invention described in JP-A-2004-140894, on the partition dividing the cooling wind tunnel, the heat radiating sections formed with cooling fins of the semiconductor device cooling units are provided so as to be arranged to face the cooling wind tunnel. Thus, the manufacturing cost can be reduced. However, for providing a drip-proof structure with the cooling wind tunnel and the electrical component mounting section divided in watertight, it is necessary to provide gaskets.
In this case, the gaskets are positioned between the opening of the case and peripheral sections of the cooling units. Hence, by adjusting tightening force of a screw, the gasket is compressed to a proper thickness so as to secure a drip-proof state.
In this way, in the example of a related electric power converter described in JP-A-2004-140894, for securing a drip-proof state, the gasket must be compressed down to a proper thickness. Thus, the compression of the gasket down to the proper thickness is carried out in such a way as to adjust a tightening force applied to a tightening piece such as a screw. The adjustment of the tightening force is often managed by making an adjustment of the torque applied by a tightening tool. In this process, however, there is an unsolved problem that the compressed thickness of the gasket is not stably determined. Moreover, there is also an unsolved problem in that a tightening torque applied to a screw sometimes becomes larger compared to the strength of a section where the gasket is secured by the screw to result in deformation of the section.
Accordingly, there are unsolved problems in the art of electric power converters for rolling stock, and with providing electric power converters for rolling stock which can allow proper compression of the gaskets to be correctly carried out, to provide a drip-proof state with the use of gaskets.